earwig, plan on doing some room treatment if you want deep bass in a 13x13 room. also, while it may not be intuitive, a stereo pair of subs will be easier to integrate into your room than a single mono sub. this is because two sources of output will better load the room than one.
you can use either powered subs or passive subs. i would recommend passive for a couple reasons - the outboard electronics are usually better; & ultimate flexibility is better. also, actively crossing your totem's will relieve them of low-bass duty; if you buy powered subs, you really do not wanna run the totem's & their amp thru a powered sub's x-over. however, if you find a decent pair of powered subs at a great price, you could always run them thru an outboard x-over, yust making sure the sub's built-in x-over is set at its highest setting, usually around 150hz or so. that way, when you set the outboard x-over to ~60hz or so, it effectively eliminates the powered sub's x-over from the equation. i actually did this once, when my system/living situation was in transition, & i wasn't able to use my vmps larger subs. i found a pair of cheap powered subs, (yamaha yst-sw305's), & effectively ran them this way, still using an active marchand x-over...
here's a cut-n-paste i made from another thread, about subs:
vmps makes killer passive subs; i defer to others for actives. but, for decent bass on the cheap, i *can* recommend looking for used yamaha yst-sw305 active subs. w/two forward-firing 8" servo-controlled drivers, these are -3db at 28hz, -10db at 20hz. in-room response will be better. i had a pair of these in a ~16x24 room, & the bass was wery good. no, not as good as my pair of vmps largers, but they're good enuff so that i didn't feel i need to spend silly money that i see some folk spending on powered subs. and, you can still use these w/an active x-over. yamaha has replaced this sub w/the yst-sw315 - a single down-firing 10"-driver sub w/the same specs. never heard it, but a buddy of mine got one for one of his non-audiophile friends, & he said it was really amazing for the money. you can get these on line (and on ebay) for ~$200 shipped...
doug s.